Series overview plot

The Doctor is suddenly thrown into a whirlwind of adventure as he regenerates in the blink of an eye, without warning. The search for the truth leads The Doctor to meet an old friend, the clever and  brilliant Cassie Smith. 

Together the are going to go across the stars, throw time and space, going into dangers unknown. 

What happens to humanity in the 42nd century? Why is everyone so into music in the 80's? What is the truth of the trees of Earth? What lurks in the deep? Who is Experiment CSSC? Why is The Doctor scared of a silent dripping tap? And What is Abyss?